What is Science? - Definition, Topics & Branches

Lesson Transcript
Amanda Robb

Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

Expert Contributor
Ana Benito Gonzalez

Ana has a PhD in Biology. She has taught college classes at leading U.S. universities, also works as a Biology tutor. She has published several scientific journals.

Science is everywhere and it includes many different interesting and complex branches. Explore the definition, branches, and different topics of science, including physics, chemistry, biology, earth science, and astronomy. Updated: 10/16/2021

What Is Science?

Science is the study of the physical and natural world through observations and experiments. Science is all around us. Right now, the fact that you exist and are in the process of reading this lesson is science. The process of creating the air we breathe - also science. The food we enjoy, water we drink, and clothes we wear are all based in science. Looking up into the atmosphere gives us a glimpse into astronomy, another branch of science. You can't get around it. Science is everywhere and is one of the most important topics of study in our world.

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  • 0:03 What Is Science?
  • 0:38 Branches of Science
  • 5:41 Lesson Summary
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Branches of Science


Science is organized from the most basic forces in nature to some of the largest, like the study of the earth and space. The study of physics focuses on laws and properties that govern behavior of all matter. Physics often involves things we can't see or touch, but can prove, like gravity. We can't see or touch gravity, but because of years of experiments, we know it's there.

Physicists also study energy, mechanics, motion, waves, electricity, nuclear reactions, and forces. People interested in physics use scientific laws and theories to build some of the things we see everyday, like bridges, cars, buildings, and power plants. If it's a structure or involves a motor, physics was surely considered when creating it.

Albert Einstein was one of the most famous physicists to date. He developed the theory of relativity, which is the basis for black holes and the potential for time travel, as well as how matter is converted to energy, which is used in nuclear power plants.


Chemistry is the study of chemical reactions and properties of matter. All the principles in chemistry are based on what we know about physics. As you can see, science topics build on each other, like a pyramid. Chemistry involves how atoms, the smallest particles of the world, bind together to create compounds. Although this might seem minor, chemistry is responsible for nearly any household product you use. Hair care products, cleaning products, even the packaged foods you eat, are all based in chemistry. For example, in the lab, scientists use chemical reactions to make compounds that smell like certain natural foods. One of the earliest discoveries was methyl anthranilate, a compound that smells like grapes and was one of the original ingredients in grape Kool-Aid.

Other chemists had a more significant impact on the world. Marie Curie was the first to discover two new radioactive elements and to use radiation to treat cancerous tumors. Her work revolutionized medicine. Unfortunately, she eventually died of radiation exposure. Before her death, she received a Nobel Prize in Chemistry, one of the most esteemed awards for scientists.


Biology is the study of life, and the principles and compounds in chemistry form the foundation for it. Biology spans from studying the most minuscule structures inside cells, called organelles, to giant masses of land with specific climates, called biomes. Biologists study cells, genetics, anatomy and physiology of the body, evolution, and ecology. Biology is perhaps the most relevant to human life, as many biologists focus on studying our bodies and the components inside them, like cells and DNA.

In fact, some of the earliest geneticists were interested in the basics of DNA. In 1953, James Watson and Francis Crick published their work on the structure of DNA inside cells, which launched the field of cellular genetics. Now, scientists working for the government and many independent companies are racing to find cures for cancer, treatments for diabetes and heart disease, and infectious diseases like HIV through studying cells and genetics.

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Additional Activities

Fun Science Experiment: How to Make a Density Tower:

No matter what type of science they study, one thing almost all scientists do is conduct experiments. Here's an experiment you can do to study density, which is the scientific term that describes how compact or dense is a substance. The density of liquids is a concept often used in several of the sciences described in the lesson, such as chemistry, physics, and biology. For example, the density in our body fluids, such as blood, has to remain constant to keep it functioning properly.

Materials you will need:

  1. Water with food coloring
  2. Milk
  3. Honey
  4. Vegetable oil
  5. Dishwashing liquid
  6. Tall straight glass
  7. Ping-pong ball
  8. Cherry tomato
  9. Bolt
  10. Turkey baster


  1. Get your tall glass and start by pouring honey (which is the densest liquid). Carefully pour about 3/4 of an inch (Same width for every layer from now on).
  2. Next, add the milk slowly with the turkey baster against the glass (not to disturb the layer of honey underneath).
  3. Add the dishwashing soap now using the turkey baster against the glass wall again.
  4. Next, add the fourth layer, the water with food coloring with the turkey baster against the wall once more.
  5. Finally add the vegetable oil, the same way.
  6. Now, you can gently drop the small objects (or similar ones): bolt, tomato and ping-pong ball.

You will observe that each object will sink to different layers in the glass. For example, the bolt will sink to the bottom because it is denser than honey. The tomato will sink until it meets the milk.


  1. What do you think will happen to the ping-pong ball?
  2. Can you predict the result?
  3. Why do you think that would happen?
  4. What do you think would happen if you tried to mixed all the liquids by shaking the glass?


The ping-pong ball will float on top of the oil since it is the less dense of these three objects.

Feel free to try any other small objects you have at hand!

Some of the liquids won't be able to mix with the others, the oil due to its properties will separate fully few minutes after you settle the glass down again.

Remember to have fun!

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